class BMC::Sorter
  include BMC::SortingHelper

  attr_reader :collection, :sort_param, :column, :direction

  def initialize(collection, sort_param = nil)
    @collection         = collection
    @sort_param         = sort_param
    @column, @direction = sortable_column_order(sort_param.to_s)
  end

  def sort
    raise NotImplementedError
  end

  def call
    # Don't replace by `collection.reorder(sort)`
    # #sort can change #collection and must be called before #collection
    order = sort
    collection.reorder(order)
  end

  def self.call(...)
    new(...).call
  end

  private

  def inverted_direction
    {asc: :desc, desc: :asc}[direction]
  end

  def joins(...)
    @collection = @collection.joins(...)
  end

  def left_joins(...)
    @collection = @collection.left_joins(...)
  end

  def by_column(c = column)
    {c => direction}
  end

  def by_lower(c = column)
    Arel.sql "LOWER(#{c}) #{direction}"
  end
end